Selectable pixel amplifier for use in a photosensor array
AssigneeXerox Corporation
InventorsPravin N. Kothari, Paul A. Hosier, Scott L. Tewinkle
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Abstract
A CMOS-based voltage signal amplifier is particularly useful for amplifying signals from a single photodiode, or a small set of photodiodes, within a large photosensitive imaging device. When the imaging device reads out image signals from a large number of photodiodes, each amplifier is selected for operation only within a very brief time window when the particular photodiode associated therewith is reading out. The amplifier of the present design is suitable for rapid power-up and power-down when it is selected and deselected.
Claims9
An amplifier suitable for processing image signals, comprising:
- an input stage having a first differential pair including two p-devices and a second differential pair, complementary to the first differential pair, including two n-devices;
- a first load device for supplying current to the first differential pair and a second load device for supplying current to the second differential pair, the first load device and the second load device being biased at a common bias node;
- self-biasing circuitry for generating a bias at the bias node;
- and
- means for deselecting the amplifier in response to an external signal, the deselecting means including means for grounding the bias node and means for eliminating current in the self-biasing circuitry in response to the external signal.
A photosensitive apparatus, comprising:
- a set of photosensors, each photosensor outputting a voltage signal relating to an intensity of light thereon;
- a set of amplifiers, each amplifier in the set of amplifiers being associated with a photosensor in the set of photosensors, for amplifying a voltage signal from the photosensor;
- and
- means for sending a deselection signal to any amplifier;
- each amplifier including
- an input stage having a first differential pair including two p-devices and a second differential pair, complementary to the first differential pair, including two n-devices;
- a first load device for supplying current to the first differential pair and a second load device for supplying current to the second differential pair, the first load device and the second load device being biased at a common bias node;
- self-biasing circuitry for generating a bias at the bias node;
- and
- means for deselecting the amplifier in response to the deselection signal, the deselecting means including means for grounding the bias node and means for eliminating current in the self-biasing circuitry in response to the deselection signal.
Dependencies are inferred from the claim text.